Electrostatic photocopying apparatus

ABSTRACT

An electrostatic photocopying apparatus having a corona discharge device positioned vertically between a projection optical unit and a copying paper stand which is associated with a developer solution container. The distance between the corona discharge device and the copying paper is maintained sufficiently large to create a weak corona discharge, and the corona discharge device is swingable out of the vertical line to allow operation of the optical unit.

United States Patent [72] Inventor 384181180 Al 3,299,787 1/1967 Kolb et al. 355/10 T0kyo,Japan 3,307,034 2/1967 Beam SSS/3X 1 mm;- 1 3 1 FOREIGN PATENTS re 0v. [45] Patented Mayzs, 1971 1,541,317 10/1968 France 355/3 [73] Assignee Kabushiki Kaisha Ricoh Primary Examiner--Samuel S. Matthews Tokyo, Japan Assistant Examiner-Richard M. Sheer [32] Priority Nov. 14, 1967 Attorney-Burgess, Ryan and Hicks [33] Japan [31] 73193/67 [54] ELECTROSTATIC PHOTOCOPYING APPARATUS 4 Claims, 1 Drawing Fig. [52] US. Cl 355/3, ABSTRACT; An electrostatic photocopying apparatus having 355/10 a corona discharge device positioned vertically between a pro- [51 I jection optical unit and a copying paper tand is as. Fleld 0 Search sociated a developer olution container The distance between the corona dischar e device and the co ying a er is [56] References C'ted maintained sufficiently la ge to create a 63k ctfrona UNITED STATES PATENTS discharge, and the corona discharge device is swingable out of Re25,779 5/1965 Giaimo, Jr. 355/3 the vertical line to allow operation of the optical unit.

PATENTED HAYES I971 INVENTOR. Byrks d'/ndd My 6 z Arra vsv f BACKGROUND. OF THE INVENTION The present invention relates to an electrostatic photocopying apparatus andmore particularly an electrostatic photoco pying apparatus wherein a copying paper is located within a weak corona discharge region.

In the electric charge device utilizing coronadischarge in corporated in the conventional electrostatic photocopyingapparatus, the coronadischarge electrodes comprising a plurality of fine wires are disposed closely to a copying paper. The corona discharge due to a high-tension voltage isproduced; between the corona discharge electrodes and the copying paper holding stand while either of the corona discharge electrodes or the copying paper holding stand is displaced relative to the other, whereby the photoconductive layer of the copying paper is positively or negatively charged. When the corona discharge is produced while the corona discharge electrodes are disposed closely to a copying paper, an extremely high contrast image can be faithfully reproduced when the original to be reproduced consists of very small dots and/or fine lines. However, when the size of the originalto be reproduced is rather large, a strong edge effect occurs and a reproduction of an image having a halftone is difficult to obtain. Furthermore, when the strong corona discharge is utilized, the developing marks tend t occur because the copying paper has not been unifonnly charged.

SUMMARY OF THE INVENTION In view of the above, the present invention provides an elec- I trostatic photocopying apparatus wherein corona discharge electrodes are associated with a copying.paper holding stand and spaced apart therefromby a relatively large distance so that the surface of the photoconductive materialsuch as zinc oxide upon a copying paper is located in a weak corona discharge region. The defects encountered in the conventional electrostatic photocopying apparatus can thereby be eliminated and a series of successive operations required for electrostatic photocopying can be effected more advantageously.

When the corona discharge electrodes are spaced apart from the copying paper by a relatively large distance and the corona discharge is generated between the corona discharge; electrodes and the copying paper holding stand,-thecopying paper may be exposed sufficiently within the dischargeregion without the necessity of relative displacement between the copying paper and the corona discharge electrodes, so that the copying paper may be maintained stationary in position upon the copying paper, holding stand and subjected to uniform and relatively weak corona discharge.

According to one preferred embodiment of the present invention, the corona discharge electrodesare spaced apart a copying paper from a considerable distance upwardly thereof so that the copying paper may be exposed in the weak corona discharge region. After the copying paper is charged, the corona discharge electrodesare retracted and the image of an original to be reproduced is projected upon the copying paper, whereby an electrostatic latentimageis. formed thereupon. After the exposure, the developing solution containerwhich is normally disposed downwardly of the copying paper holding stand is moved upwardly so that the latent image may be developed in this solution.

According to another embodiment of the present invention, a plurality of developingsolution coritainers may be provided so that the, exposed copying paper may be processed with a, plurality of processing solutions. In this case, said pluralityof solution containers are disposed in the order that ,theexposed. copying paper is processed successively. For example; the processing solution containers are successively conveyed as will be described in more detail hereinafter in the predetermined order so that the exposed copyingpaper may be processed successively with, the conveyed processingsolution.

2 I Other objects and advantages of the present invention will become apparent from the following description of a preferred embodiment thereof taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF DRAWING A single FIG. is a side view of an embodiment of an electrostatic photocopying apparatus according to the present invention.

DESCRIPTION OF THEPREFERRED EMBODIMENT A vertical supporting column 2 fixedly secured to a stand 1 carries an exposure device 4 in which are disposed a light source for projection, acondenser lens (both of which are not shown) and a projection lens 3; a charging device generally indicated by 6 having a suitable number of needle-shaped coronadischargeelectrodes 5; and a copying paper supporting device 9 having a copying paper supporting stand 7 and a bias electrode plate 8. Upon the stand 1 is disposed a developing solution container elevating device 11 which is adapted to move vertically a developing solution container 10 which has an aperture large enough to receive therein said copying paper holding stand 7.

The projection optical system conventionally used in the enlarger may be used as the aforementioned exposure device 4. Reference numeral 12 designates a diapositive held in a cassette (not shown) which is set in the exposure device 4.

An electrode supporting member 13 of the charging device 6 is swingably attached to the extreme end of an arm 14 attachedmovably in vertical to the supporting column 2, and can be swung about a shaft 15. Therefore, when the exposure device 4 is used, the supporting member 13 is retracted as shown by the broken'line 13a so that the effective exposure by the lights from the exposure device 4 to a copying paper 16 is not prevented. A knob 17 screwed to the back portion of the arm 14 serves to hold the arm I4 stationary after the height of the arm 14 has been suitably adjusted.

At the upper end of an elevating shaft l9.loosely fitted into a cylinder 18 .whichin turn is securely fixed to the lower surface of the stand .1 is securely fixed a receiving stand 19a which is elongated in the direction perpendicular to the surface of thecopying paper 16. Upon the receiving stand 19a is disposed ,a sliding-plate 20 upon which is securely fixed the developingsolution container 10. One end 220 of a lever 22 pivoted by means of a pivot 21 to a position of the stand 1 on the side of the operator extends below a pin 1% which is fitted into an elongatedslot 18a of the cylinder 18. The pin 19b is securely fixed to the peripheral surface of the elevating shaft 19 and is adapted to be pushed up by means of the one end 22a. of the lever 22 when the lever 22 is rotated in the direction indicated by the arrow so that the developing solution containerlO may be moved upwardly.

When the height of each corona discharge electrode 5 is adjusted and supplied with a high-tension voltage in order that the copying paper is subject to the corona discharge in the best possiblestate, the whole surface of the photoconductive layer, of the copying paper is uniformly charged. The aforementioned'the best possible state" infers that the copying paper is positioned in the weak corona discharge region where the charge density'is uniform and which is spaced apart from the electrodes 5 by a relatively large distance. When the distance between the. electrodes to which is supplied a hightenslon voltage sufficiently high enough to cause corona disc arge and a ground plate (which is the copying paper holding stand in .the FIG.) is less than a few centimeters, no weak corona discharge. region occurs. However, when the distance is increased to the range from 10 to 50cm., then the weakcorona-discharge. region is generated externally of the strohgcorona discharge region in the form of a cylinder having a diameter of the range from 5 to 15 centimeters.

Next, the electrode supporting member 13 is retracted toward the position indicated by the broken line 13a and the chargedcopyingpaper is exposed, whereby an electrostatic v latent image is forrnedthereupon. Thereafter, the bias electrode plate 8 is placed in the position indicated by the broken line 8a upwardly of the copying paper. The developing solution container 10 is moved upwardly so that the copying paper holding stand 7, the copying paper 16 and the bias plate 8 are immersed in the developing solution, whereby the developing process is accomplished.

When a plurality of developing solutions such as prewet solution, rinse solution or color developing solution are used, a predetermined number of containers containing such solutions are arranged upon the sliding plate which in turn is moved toward or away from the receiving stand 19a so that a required developing solution may be placed downwardly of the copying paper holding stand 7 and then moved upwardly,

whereby the developing process may be accomplished in this solution.

As described hereinabove, according to the present invention, the discharge device is spaced apart from the copying paper holding stand so that the copying paper may be located within the weak corona discharge region. Therefore, a faithful reproduction of an image without any edge effect can be obreproduced image can be obtained. As to means for retracting the charging device from the light path for effective exposure of the copying paper, the electrode supporting member may be rotated about the supporting column instead of swinging the supporting member away from the light path as described above. Furthermore, the exposure device 4 may be disposed laterally of the column 2 by disposing suitable reflecting mirror upwardly of the charging device, instead of being disposed immediately above the copying. paper holding stand as described hereinabove.

' The present invention has been described with a particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications may be effected within the spirit of the present invention as described hereinabove and as defined in the appended claims.

Iclaim:

1. An electrostatic photocopying machine having a corona discharge device and comprising: a main stand;

a vertically positioned supporting column mounted on said main stand;

a projection optical unit having a light source for directing light vertically downwardly, said unit mounted on the upper part of said column;

a copying paper support stand mounted on the bottom part of said column in vertical alignment with said optical unit and adapted to have copying paper placed thereon;

the corona discharge device being mounted on said vertical column between said optical unit and said copying paper support stand and in vertical alignment therewith, said discharge device spaced a predetermined distance from said support stand to create a weak corona discharge region for said copying paper,

container means having developing solution therein and located adjacent to and below said copying paper support stand in vertical alignment thereof, said container means positioned on said main stand, and means provided to selectively move said container means upwardly so that said support stand and copying paper are immersed in said solution; a bias electrode plate pivotally mounted on said column adjacent the mounting of said support stand, said bias electrode plate being pivoted to an inactive vertical position when said corona device is operable, and said bias electrode plate being pivoted to an active horizontal position to be immersed in said developing solution when said container means has been moved upwardly; and

said corona discharge device being pivotally mounted and swingable to an inactive substantially vertical position thereby exposing said copying paper to the downwardly directed light when the optical unit is operable.

2. A photocopying machine according to claim 1, in which said container means is of a predetermined size to allow simultaneous immersion therein of said support stand, copying paper and bias electrode plate.

3. A photocopying machine according to claim 1, in which said container means is mounted on a slidable plate that is positioned on said stand, and said container means comprises a plurality of containers filled with different solutions for different developing treatments, said plate being slidable and vertically movable to sequentially immerse the copying paper in each container.

4. A photocopying machine according to claim 1, in which the predetermined distance that said discharge device is spaced from said support stand is in the range of l050 centimeters. 

1. An electrostatic photocopying machine having a corona discharge device and comprising: a main stand; a vertically positioned supporting column mounted on said main stand; a projection optical unit having a light source for directing light vertically downwardly, saId unit mounted on the upper part of said column; a copying paper support stand mounted on the bottom part of said column in vertical alignment with said optical unit and adapted to have copying paper placed thereon; the corona discharge device being mounted on said vertical column between said optical unit and said copying paper support stand and in vertical alignment therewith, said discharge device spaced a predetermined distance from said support stand to create a weak corona discharge region for said copying paper; container means having developing solution therein and located adjacent to and below said copying paper support stand in vertical alignment thereof, said container means positioned on said main stand, and means provided to selectively move said container means upwardly so that said support stand and copying paper are immersed in said solution; a bias electrode plate pivotally mounted on said column adjacent the mounting of said support stand, said bias electrode plate being pivoted to an inactive vertical position when said corona device is operable, and said bias electrode plate being pivoted to an active horizontal position to be immersed in said developing solution when said container means has been moved upwardly; and said corona discharge device being pivotally mounted and swingable to an inactive substantially vertical position thereby exposing said copying paper to the downwardly directed light when the optical unit is operable.
 2. A photocopying machine according to claim 1, in which said container means is of a predetermined size to allow simultaneous immersion therein of said support stand, copying paper and bias electrode plate.
 3. A photocopying machine according to claim 1, in which said container means is mounted on a slidable plate that is positioned on said stand, and said container means comprises a plurality of containers filled with different solutions for different developing treatments, said plate being slidable and vertically movable to sequentially immerse the copying paper in each container.
 4. A photocopying machine according to claim 1, in which the predetermined distance that said discharge device is spaced from said support stand is in the range of 10-50 centimeters. 